The present invention relates to a method and device for controlling the glottic opening and airway in animals. Controlling the opening and closing of the vocal cords, and hence the airway, by way of a simple non-invasive technique and device therefor has far-reaching implications, not only in the field of otolaryngology, but also in the fields of anesthesiology and emergency medicine as well.
Direct stimulation of the recurrent laryngeal nerve (RLN) results in a characteristic movement of the vocal cords that is frequency dependent. In 1961, Nakamura in a paper entitled "Movement of the Larynx Induced By Electrical Stimulation of The Laryngeal Nerves" presented at the Upstate Medical Center of the State University of New York, in Syracuse, N.Y., May 29-June 3, 1961, and published in Brewer, Research Potentials in Voice Physiology, pages 129-136, N.Y. State University Press, 1964, demonstrated that in situ bilateral electrical stimulation of the RLN at a frequency of 20 Hz resulted in vocal cord abduction, while stimulation at frequencies greater than 40 Hz resulted in vocal cord adduction and a closed glottis. However, inasmuch as the experiments were conducted on dogs which were under operation with an exposed RLN and anesthetized, the clinical significance of these results remained obscure. To date clinical application of direct RLN stimulation has been proposed solely to aid surgeons in locating that nerve so that inadvertent damage of it can be avoided during surgery.
At the present time there is no easy method of controlling vocal cord position for diagnostic or therapeutic purposes. Current techniques involve mechanical methods such as pushing the vocal cord to assess arthritis or blowing increased air pressure through the larynx in cases of laryngospasm to attempt opening of the glottis. Transcutaneous or transmucosal stimulation of the RLN has not previously been proposed as a method for controlling vocal cord position in lieu of the methods described above. Yet, transcutaneous or transmucosal stimulation of nerves in other areas of the body is an established and consistently used therapeutic tool. See, e.g. Scand. J. Urol. Nephrol. (Suppl.) 44, pp. 31-41 and 55-63 (1978). Such stimulation has also been used, for example, by neurologists as a method for alleviating pain and as a means for diagnosing disorders of the spinal cord and peripheral nervous systems. In addition, physiatrists have utilized transcutaneous or transmucosal stimulation to facilitate muscle reeducation.